The killer fired 10 times. Nine shots hit Lanny Horwitz, leaving him in a pool of blood as he took a shower in the bathroom of his Jupiter, Fla., home.

Radley, his son, a former gun dealer, said he heard the gunshots, but had no idea who pulled the trigger. Meanwhile, down the hall was Horwitz’ ex-wife, Donna, whose relationship with her former husband was chaotic at best.

Police soon learned that Radley, too, had a rocky relationship with his father.

“Not only was he murdered, he was murdered with such indifference,” says Lanny’s brother, Barry Horwitz. “He died like Caesar, surrounded by enemies.”

When investigators arrived at the crime scene, Radley Horwitz was described as being stoic, while Donna Horwitz was visibly upset.

“I had no idea what happened until I – I heard my mother screaming,” Radley Horwitz tells 48 HOURS. “And then more shots, and they were pretty, pretty rapid.”

What the investigation would uncover was a deeply troubled family struggling with debt, a father with an unusually close relationship with a female business partner, and a patriarch who allegedly was hard on his son and his ex-wife.

Growing up in Buffalo, Lanny Horwitz was focused on success at an early age, according to Barry Horwitz. Lanny went on to marry Donna in 1967 and the couple had one child. They divorced in May 2001, remarried in September 2001 and divorced again in June 2002. But by the time they were back together in 2011 – living as a family in a wealthy development in Florida – Lanny had lost much of his fortune and had asked Donna for a $200,000 loan.

But who killed him and why? There were two suspects right in the home and potentially others outside. Radley had a troubled past, including a stint in prison, and police found he once owned a book titled Hit Man: A Technical Manual for Independent Contractors. Donna, meanwhile, was distraught over Lanny’s relationship with a female business partner. Radley, a gun dealer, had an arsenal in the home, and his mother even had her own gun.

“It boils down to a motive as old as time, and that’s love, hate and obsession,” says Assistant State Attorney Aleathea McRoberts.

Van Sant and 48 HOURS piece together the murder of Lanny Horwitz through interviews with Radley Horwitz, Barry Horwitz, police investigators and prosecutors.